Wood Movement

[Ruffnek]

Does anyone except me think the issue of wood movement in furniture is exaggerated?

Kevin's night stand and his method of attaching the top with pocket screws is an example. I feel that in today's climate controlled homes, that wood movement is minimized so that he is perfectly safe in using that method. Even if the wood moves slightly, so do the screws. If he were to glue it cross-grain on that wide an area then it might split the top. I say might because again, the wood is not seeing the broad swings in temperature and humidity that furniture used to see.

If a piece of furniture were built in Florida and then moved to Arizona, there would likely be problems, regardless of construction methods used. But, if properly dried (<10% MC) wood is used and the piece stays in a similar environment is wood movement really a big consideration?

FWIW, I'll keep using construction methods that accommodate wood movement...that's just good practice...but even while doing so, I'll wonder how much it's actually necessary in most cases.

Just wondered what the group here thinks about the subject.

[RiverWalker]

I was wondering about this too, to some extent.

in my reading it seems rather inconsistent, some things seem to depict considering for wood expansion/contraction as being a big, complex issue that requires extensive planning and expertise.

and other places seem to almost completely disregard it as an issue at all.

'tis a bit confusing for the new person.

[sachbvn]

I can think of four different things that had a decent sized top that I used pocket screws to attach the top to the sides.... never a problem. The first is a couple years old now.

When I made my first coffee table and attached the top using pocket screws - guys at ww.com were just down right certain it would split..... haven't had a problem with it yet.... I didn't even use enlarged holes or anything.


Zac

[Mark]

My $.02

Turned an Ice Cream Scoop handle, and assembled it here in the Northwest. Wood was ambient MC for here. The assembly included a brass ferrule at the scoop end, which was set tight. Sent it to my dad in Colorado as a gift, and within a month, the ferrule came loose due to the shrinkage.

So, it probably makes most difference, if the furniture you build will reside where you build it.

Mark

[TDHofstetter]

It depends. The humidity inside any more-or-less typical Vermont house may swing as wildly over the course of a single year as the mean climatic humidity is different between Arizona and Florida.

During the winter, most of us heat with some sort of combustion heat... and the outdoor air, drawn in to replace the air lost to combustion, is extremely dry because it's below the freezing point of water. Work as we do to humidify, we have a difficult time reaching a level in excess of about 25; lots of folks never see that high a humidity during the winter.

Something similar happens in late August & early September, when all our wells threaten to run dry.

During the spring & early summer, on the other hand, and also at the very early onset of winter, our outdoor humidity runs very high... like enough to settle dew deep enough to spoon up. Not so much in early winter, but during spring & summer we tend to leave our windows open for "fresh air". As a result... bedsheets are often found nearly as moist as a dishrag.

I've had some pretty serious experiences with wood movement since I've lived here. I built a tinderbox around a piece of super-heavy stovepipe once, leaving myself plenty of rabbet to accept the pipe. Overall, it was just over 8" square, with the round 6" stovepipe hole in the center. I made the face from four pieces of red oak, each piece turned diagonally so the grain ran from the center of the hole radially out to all four corners.

I built that in the summertime and installed it in the kitchen cabinets. By the middle of next winter, two of those diagonal red oak face pieces had split, leaving gaps nearly wide enough to stick a pencil through. I left 'em alone, and by the middle of the next summer, the gaps had closed tightly again.

'T'was put together like this:



The two leftmost pieces split.

[sawduster]

I've had some pieces that I sent to my folks in the desert of West Texas that have some issues while like items that stayed here didn't. Like has been said, if it is not going to be moved to a radically different climate, a problem could arise.

For table tops, I use wooden buttons along the connecting surfaces between the cross grained wood, or I'll allow for expansion in a particular direction, but I've not noticed any sort of issues even with breadboard ends on table tops where two different woods were used.

[dicklaxt]

In my opinion yes it will move,most folks don't
have HVAC in their shops so at the outset you are building in a change clause,,,,,,,,,be safe, allow for it and seal both sides of a board as it is just another place where humidity plays havoc with your handy work if left open to the surrounding air.

dick

[rrich]

One of my first projects was a TV stand for a small TV and VCR. The TV would swivel as would the VCR on the top of a cabinet. It was maybe 24" wide.

Inside the cabinet, I used 1/4" red oak for the floor shelf. I assembled the cabinet using M&T joints and put the shelf into a dado groove. Well before finishing even, the weather changed. We went from our usual summer season into our after Thanksgiving rainy season. The bottom shelf expanded in less than a week to break a couple of the M&T joints.

I had to use a clamp to break a couple more M&T joints to get the shelf out and cut in half to allow for wood movement.

BTW - Gorilla glue sucks when used for M&T joints.

[brburns]

I think that pocket hold screws (especially if you move the bit back and foth some) will allow enough movement on most table tops. I have used them in several peices. Most of the time, wood isn't going to move a half mile, it's really tiny, so leave some room.

[Safetyboy]

May 15, 2010 16:26:06 GMT -6 brburns said:

I think that pocket hold screws (especially if you move the bit back and foth some) will allow enough movement on most table tops.

That was my plan (hope?) on the nightstand. Though I didn't follow plans, the pictures I saw did show the tops pocket-screwed on, so I did copy that detail ('course just because I saw pictures of it doesn't mean it's "correct" either, but it seemed reasonable).

The tricky thing with the nightstand is that the top of the top drawer is flush with the underside of the table top in the design - I liked that look and wanted to keep it, so that ruled out using the wooden buttons or other methods that might get in the way.

BTW, the photos I copied said his were "Stickley No. 110 reproductions" - I wonder how Stickely would have attached a top in this design?

[Stretch]

It has been my experience that allowing for wood movement is highly over hyped. The rules for allowing for movement were created when most lumber was either only airdried or worked green. Kiln dried wood is just so much more stable. If you use a modern finish you don't have to worry about wood movement nearly as much. Is it still a consideration? Absolutely. Not to consider it is stupid. At the same time though, looking at the online calculators for wood movement is going to make you freak out. Wood finished with a modern finish isn't going to swing in moisture content very much even if there are large changes in the environment.

[dcarter636]

I think that when you are building with one kind of wood and pay some attention to grain orientation there isn't much of an issue to fuss over, except on large stick and cope door panels where some perpendicular orientation is unavoidable.

Mixing different species is altogether another story. Our RH varies from 10% to 70% every year and gluing hunks of hygroscopically dissimilar woods together can quickly cause mischief.

I probably fuss over this more than most folks because it is very much like dealing with thermal expansion which was/is a key to making precision mechanisms behave all the time, habit dies hard with old fire horses.